Climate changes will impact forests/maple industry

February 6, 2013

For many of the region's maple syrup producers, the 2012 sugaring season was unlike any they'd ever experienced. Several of the smaller producers I spoke with last year told me that it was their worst season ever. A few said it lasted literally one, or less than one week. A few didn't even bother to tap. According to the Department of Agriculture National Agricultural Statistics Service, syrup production in New York state decreased by more than 36 percent; from 564,000 gallons with a value of just over $22 million in 2011, to 360,000 gallons with a value of just under $12.3 million in 2012.

We had an unusually warm winter last year. I can recall a friend of mine lightheartedly calling January, March-uary. And the month of March felt more like May. In fact, scientists at the National Oceanic and Atmospheric Administration said it was the warmest March on record for all of the lower 48 states (and the government has been keeping records since 1895).

Daytime high temperatures in our region ranged from the high 60s through the low 80s for weeks, shattering previous records on a nearly daily basis. Nighttime low temperatures remained where maple syrup producers would've liked daytime highs to have been.

Sugaring is a weather-related industry. Production hinges on the freezing nights and daytime thaws that cause sap to run. Fewer freeze-thaw days translates to fewer sap runs which, in turn, translates to less syrup being produced. Optimum sap production occurs when nighttime temperatures fall into the 20s and daytime temperatures range in the 40s, preferably with sunny skies, allowing the season to gradually transition from winter to spring.

In recent years, scientists at Cornell University, at the University of Vermont's Proctor Maple Research Center, and elsewhere have been looking closely at changes in the onset and duration of the maple sugaring season. In testimony before Congress in 2007, Proctor Maple Research Center director Timothy Perkins said the Vermont sugaring season now begins about 8 days earlier and ends about 11 days earlier than it did 40 years ago. A Cornell study, which was funded by the New York State Agricultural Experiment Station and NOAA, and completed in 2010, looked at the relationship between sap flow and temperature at thousands of locations from North Carolina to Quebec and as far west as Minnesota. Those researchers also determined that starting dates for tapping maples in the Northeast are now about a week earlier than in 1970. By scaling down global climate computer models to regional scales, in order to project localized daily temperatures into the year 2100, the Cornell study concluded, as well, that in northern regions like ours, the overall number of sap flow days probably won't change much. The peak season, however, will continue to shift; becoming earlier and earlier over time.

In an article written by Cornell University life sciences writer Krishna Ramanujan, published in the Nov. 10, 2010 edition of the Cornell Chronicle, Brian Chabot, a professor of ecology and evolutionary biology who co-authored a paper on climate change and maple sugar production, which appeared in the journal Climate Change in September of that year, is quoted as saying, "By 2100, we can expect to begin tapping maples closer to Christmas in the Northeast." The article goes on to say that, according to Chabot, maple syrup production in Quebec may actually benefit from climate changes.

The picture is quite different, however, for producers in locations at the southern end of the sugar maple range. Rumanajan's article goes on to say that Chabot believes that maple production south of Pennsylvania will likely be lost by the year 2100, due to lack of freezing. And studies conducted by the United States Forest Service indicate a substantial reduction in suitable habitat for sugar maple in this century, with the southern range being most profoundly affected. Those studies suggest that the viability of syrup production could be further impacted as trees become more stressed by extreme weather and resulting disease and insect pressure.

Following a comprehensive review of more than 50 years of long term data on environmental conditions at the USFS Hubbard Brook Experimental Forest in New Hampshire, a group of 21 scientists recently released a paper maintaining that winters there are becoming both shorter and milder; that over that period of time, there has been a rise in the amount of rainfall and a decrease in snowfall; and that soil thaw is no longer closely tied to spring plant growth, creating a transitional period that results in the loss of important soil nutrients. The report also states that, in the absence of an insulating snow pack, exposed soils are more susceptible to freezing, which damages tree roots. As a result, there has been an increase in mortality. The study concludes, as well, that sap yields have been reduced, apparently as a result of warming winters.

A 2002 Environmental Protection Agency Climate Action Report notes that "climate change is likely to cause long-term shifts in forest species, such as sugar maples, moving north out of the country." And a study conducted by the USFS, which looked at on-the-ground movement based on latitude, not computer modeled simulations, confirms the northward movement of 40 major tree species growing in 30 eastern states. The results of that study, which looked at 15 northern species, 15 southern species, and 10 species found in both regions, were published in 2009 in the journal Forest Ecology and Management and determined that 11 of the 15 northern species have shifted North by latitude. When commenting about the study, Chris Woodall, of the Forest Service's Northern Research Station in St. Paul, Minn. said, "This is no longer conjecture."

Maples, like poplars, ashes and several other deciduous species, have seeds that are light enough to be dispersed over several miles by wind. As such, they can expand their range comparatively easily and quickly. As sugar maples migrate north (and to higher elevations), those left behind in warmer environments will eventually be displaced by better adapted, faster growing species, like oak and hickory.

Migration of tree species is nothing new. For example, in response to changes in climate toward the end of the last ice age, forest communities gradually migrated northward in the wake of receding glaciers. The current northern migration, however, appears to be occurring at an unprecedented rate.

Whatever the cause, the effects of a changing climate (e.g. heat stress, decreased soil moisture) are likely to significantly impact many of our commonly occurring tree species. And maple syrup production is not the only agricultural industry likely to be adversely affected as climates shift.